A friend asked me to help paint their house. i would have to bring my 4m old. would it be dangerous for her to be around the fumes?

Better not: If you can keep her at a good distance and still can observe her, that would be fine, if not better keep her away from the fumes or any working area

Depends: Most indoor paints are latex & considered non toxic. Some smaller infants are more sensitive to fumes than other and can develop congestion and a cough if these are noticeable. The basic rule is if you can smell it,good or bad, it can make baby congested/cough.